<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div {
            width: 0px;
            height: 0px;
            border: 20px solid red;
            border-bottom-color: blue;
            border-right-color:yellow;
            border-left-color: pink;
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>